System and method for regenerating a diesel particulate filter in a motor vehicle while parked

ABSTRACT

A system and method for initiation and control of passive regeneration ( 38, 38 B) of a diesel particulate filter ( 34 ), and the integration of that regeneration strategy with an active regeneration strategy ( 36 ) and a strategy ( 40, 40 A,  40 B) for inhibiting passive regeneration. Passive regeneration can be initiated by driver actuation of an instrument panel switch while the vehicle is parked with the engine idling provided that certain conditions confirming that the vehicle is parked and the engine is at proper temperature are satisfied. Control of passive regeneration includes a timing function that sets minimum and maximum times.

REFERENCE TO RELATED APPLICATIONS AND PRIORITY CLAIMS

This application claims the priorities of Provisional Application Nos.60/780,535, and 60/780,586, both filed on 9 Mar. 2006.

FIELD OF THE INVENTION

This invention relates generally to emission control systems in motorvehicles, such as trucks, that are powered by internal combustionengines, more particularly diesel engines that have certain exhaust gastreatment devices for treating exhaust gases passing through theirexhaust systems. The invention especially relates to a system and methodfor controlled regeneration of an aftertreatment device, especially adiesel particulate filter, (DPF) when a vehicle is parked.

BACKGROUND OF THE INVENTION

A known system for treating exhaust gas passing through an exhaustsystem of a diesel engine comprises a diesel oxidation catalyst (DOC)associated with a diesel particulate filter (DPF). The combination ofthese two exhaust gas treatment devices promotes chemical reactions inexhaust gas and traps diesel particulate matter (DPM) as exhaust flowsthrough the exhaust system from the engine, thereby preventingsignificant amounts of pollutants such as hydrocarbons, carbon monoxide,soot, SOF, and ash, from entering the atmosphere.

A DPF requires regeneration from time to time in order to maintainparticulate trapping efficiency. Regeneration involves creatingconditions that will burn off trapped particulates whose uncheckedaccumulation would otherwise impair DPF effectiveness.

The creation of conditions for initiating and continuing regenerationgenerally involves elevating the temperature of exhaust gas entering theDPF to a suitably high temperature. Because a diesel engine typicallyruns relatively cool and lean, the post-injection of diesel fuel can beused as part of the strategy to elevate exhaust gas temperaturesentering the DPF while still leaving excess oxygen for burning thetrapped particulate matter.

When a vehicle is being driven in a way conducive to DPF regeneration,such as at highway speed, the regeneration process may be conducted withlittle or no significant effect on vehicle driveability, and istypically initiated automatically by a regeneration initiation strategy.Regeneration occurring under these circumstances may be referred to as“active” regeneration.

However, elevation of exhaust gas temperature for initiating “active”DPF regeneration may not always be appropriate for the manner in which avehicle is being operated.

SUMMARY OF THE INVENTION

The present invention is directed toward a system and method forenhanced “passive” DPF regeneration under circumstances where “active”regeneration may be considered inappropriate.

“Passive” regeneration refers to regeneration that results insignificantly lower temperature for exhaust gases exiting the DPF thanwould be the case for “active” regeneration.

Consequently, the inventive system and method are considered suitablefor DPF regeneration with the engine running while the vehicle isparked. The lower tailpipe temperatures may avoid the use of temperaturereduction devices, or when such devices are used, may allow them to besmaller than if active regeneration were to be allowed when the vehicleis parked.

Briefly, the invention involves using essentially nitrogen dioxide-basedregeneration for passive DPF regeneration instead of the essentiallyoxygen-based regeneration that characterizes active DPF regeneration.Temperatures of exhaust gases leaving the DPF during passiveregeneration are in the range of 350° C. to 400° C., a range that isconsiderably lower than the range for active regeneration.

When a vehicle is parked with the engine running, the driver can initatepassive regeneration manually, such as by operating a switch. The enginecontrol system will begin to operate the engine in a way that will forcepassive regeneration. One aspect of this involves re-setting certainset-points in the control system to values that will initiate passiveregeneration as the engine continues to run. Parameters whose set-pointsmay be reset include: engine idle speed, main fuel injection timing, EGRvalve position, turbocharger vane position, intake throttle position,post-injection fuel quantitiy, and post-injection fuel timing.

For creating a suitable abundance in NO_(x) in exhaust gas entering theDPF, the control system acts on the EGR system in a way thatdramatically reduces EGR, even to the point of shutting off EGR. Theintake throttle operation aids in elevating exhaust gas temperature.Post-injection can be used, but with set-points appropriate for passiveDPF regeneration.

When the passive regeneration strategy is invoked, the control systemlocks out the active regeneration strategy.

Pertinent exhaust temperature and engine data may be obtained fromexisting sensors and data processing.

In accordance with principles of the invention, passive regeneration isperformed while the vehicle is parked with the engine running at lowidle speed in accordance with a low idle speed control strategy.

One aspect of the invention relates to a diesel engine comprising anexhaust system through which exhaust gases created by combustion incombustion chambers pass to atmosphere and which comprises anafter-treatment device that treats the gases before leaving the exhaustsystem but that at times requires regeneration by elevation oftemperature of the gases to a regeneration temperature range.

An engine control system processes various data to control variousaspects of engine operation for conditioning the gases to causeregeneration of the after-treatment device.

The control system comprises a first regeneration strategy forconditioning the gases to cause oxygen-based regeneration of theafter-treatment device and a second regeneration strategy forconditioning exhaust gases to cause nitrogen dioxide-based regenerationof the after-treatment device when the engine is operating at low idlespeed in accordance with a low idle speed control strategy.

Another aspect relates to a method for regenerating an exhaustafter-treatment device in an exhaust system of a diesel engine. Themethod comprises: operating the engine to create exhaust gases forcausing nitrogen dioxide-based regeneration of the after-treatmentdevice upon concurrence of conditions precedent that include aregeneration-initiation device for initiating such a regeneration beingin a condition for initiating such a regeneration, the engine operatingat a low idle speed in accordance with a low idle speed controlstrategy, and engine temperature condition being sufficiently high toinitiate nitrogen dioxide-based regeneration.

Still another aspect relates to a diesel engine comprising: an exhaustsystem through which exhaust gases created by combustion in combustionchambers pass to atmosphere and which comprises an after-treatmentdevice that treats the gases before leaving the exhaust system but thatat times requires regeneration by elevation of temperature of the gasesto a regeneration temperature range.

An engine control system processes various data to control variousaspects of engine operation for conditioning the gases to causeregeneration of the after-treatment device.

The control system comprises a regeneration strategy for conditioningexhaust gases to cause nitrogen dioxide-based regeneration of theafter-treatment device when the engine is operating at low idle speed inaccordance with a low idle speed control strategy.

The foregoing, along with further features and advantages of theinvention, will be seen in the following disclosure of a presentlypreferred embodiment of the invention depicting the best modecontemplated at this time for carrying out the invention. Thisspecification includes drawings, now briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a basic schematic diagram of portions of a diesel enginerelevant to the present invention.

FIG. 2 is a general regeneration strategy diagram embodying principlesof the present invention.

FIGS. 3A and 3B collectively show more detail of a portion of thestrategy of FIG. 2.

FIG. 4 shows more detail of another portion of the strategy of FIG. 2for inhibiting regeneration under certain conditions.

FIG. 5 is a general diagram showing another embodiment of strategy forinhibiting regeneration under certain conditions.

FIG. 6 is a diagram useful in explaining certain principles relating tothe strategy shown in FIG. 5.

FIG. 7 is a state diagram showing possible operational statescorresponding to zones of the diagram of FIG. 6.

FIG. 8 is another general regeneration strategy diagram embodyingprinciples of the present invention.

FIG. 9 shows more detail of a portion of the strategy of FIG. 8.

FIG. 10 shows more detail of another portion of the strategy of FIG. 8.

FIG. 11 is a state diagram showing possible operational states for thestrategy of FIG. 8.

FIG. 12 shows an example of a strategy for controlling a representativeparameter relevant to the regeneration process.

FIGS. 13, 14, and 15 show a general regeneration strategy similar to theones that have been described.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a schematic diagram of an exemplary diesel engine 10 forpowering a motor vehicle. Engine 10 has a processor-based engine controlsystem (ECS) 12 that processes data from various sources to developvarious control data for controlling various aspects of engineoperation. The data processed by control system 12 may originate atexternal sources, such as sensors, and/or be generated internally.

Control system 12 controls the operation of electric-actuated fuelinjectors 14 that inject fuel into engine combustion chambers 16. Aprocessor of control system 12 can process data sufficiently fast tocalculate, in real time, the timing and duration of injector actuationto set both the timing and the amount of fueling for main andpost-injection.

Engine 10 further comprises an intake system 18 through which charge airenters combustion chambers 16, and an exhaust system 20 through whichexhaust gases resulting from combustion leave the engine. Intake system18 comprises a throttle valve 22, the compressor portion 24 of aturbocharger 26, and an EGR valve 28. Exhaust system 20 comprises theturbine portion 30 of turbocharger 26 and after-treatment devices 32,34, the latter being a DPF.

From time to time, DPF 34 must be regenerated in order to purge it oftrapped particulate matter so that it can remain effective to trapparticulate matter as the engine continues to run.

The inventive method for control of DPF regeneration is performed bysuitable algorithms implemented in ECS 12 to process various data fromvarious sources.

The strategy shown in FIG. 2 comprises an Active DPF RegenerationControl Strategy 36, a Passive DPF Regeneration Control Strategy 38, andan Inhibit Strategy 40 for Inhibiting Passive DPF Regeneration ControlStrategy 38.

Active Strategy 36 comprises a strategy for oxygen-based regeneration ofDPF 34, a strategy that is typically used when a vehicle being propelledby engine 10 is being driven over the road.

Passive Strategy 38 comprises a strategy for nitrogen dioxide-basedregeneration of DPF 34, a strategy that can be used when the vehicle isparked with the engine running.

Inhibit Strategy 40 comprises a strategy for inhibiting Passiveregeneration.

The detailed strategy diagrams shown in the drawings employ certainstandard logic symbols including symbols for comparison and switchfunctions. The fact any logic symbol may by itself suggest certainrelationships for certain conditions is not meant to imply that suchrelationships for the specific conditions involved in the strategiesshown here apply. The applicable relationships are set forth in thedetailed written description presented here.

Strategy 38 comprises an AND logic function 42 shown in FIG. 3A. Allinputs to AND logic function 42 must be satisfied (logic “1's”) for thefunction to enable passive regeneration to be performed. Such enablementis signaled by parameter LV_ENA_STA_RGN (see FIG. 3B) being a logic “1”.A delay function 44 imparts a slight delay in enabling passiveregeneration after AND logic function 42 has been satisfied.

When LV_ENA_STA_RGN changes from a logic “0” to a logic “1” after thedelay, a timer function 46 is also started to begin timing the durationof passive regeneration enablement. Maximum and minimum times forpassive regeneration enablement are set by parameters C_T_MAX_STA_RGNand C_T_MIN_STA_RGN. Respective comparison functions 48 and 50 comparethe time elapsed on timer function 46 with the respective parametersC_T_MAX_STA_RGN and C_T_MIN_STA_RGN.

As long as the elapsed time is equal to or less than C_T_MAX_STA_RGN,the output of function 48 is a logic “0”. Once the elapsed time becomesgreater than C_T_MAX_STA_RGN, the output of function 48 becomes a logic“1”.

As long as the elapsed time is less than C_T_MIN_STA_RGN, the output offunction 50 is a logic “0”. Once the elapsed time equals or exceedsC_T_MIN_STA_RGN, the output of function 50 becomes a logic “1”.

The output of function 50 forms one input to an AND logic function 52.The other input to AND logic function 52 is the output of anothercomparison function 54. The outputs from AND logic function 52 andcomparison function 48 are inputs to an OR logic function 56.

The two inputs to comparison function 54 are parameters STATE_EGBP_PFand C_STATE_EGBP_PF_STOP_STA_RUN. The former parameter is an indicationof the extent to which DPF 34 is loaded with trapped particulates, andmay be measured in any suitably appropriate way. The latter parameterrepresents a threshold value for DPF loading that distinguishes betweenthe presence and absence of a need for DPF regeneration.

When STATE_EGBP_PF is less than C_STATE_EGBP_PF_STOP_STA_RUN, the outputof function 54 is a logic “0”. When STATE_EGBP_PF is equal to or greaterthan C_STATE_EGBP_PF_STOP_STA_RUN, the output of function 54 is a logic“1”.

Once passive regeneration has been enabled, functions 50, 52, and 54coact to force the output of logic function 52 to logic “0” while timingfunction is timing the minimum time set by C_T_MIN_STA_RGN. Once thatminimum time has been equaled and exceeded, the output of logic function52 is determined by the presence or absence of a need for continuingregeneration. A need for continued regeneration, as signaled by theresult of comparing STATE_EGBP_PF and C_STATE_EGBP_PF_STOP_STA_RUN, willcause the output of logic function 52 to remain logic “0”. Absence of aneed for regeneration, as signaled by the result of comparingSTATE_EGBP_PF and C_STATE_EGBP_PF_STOP_STA_RUN, will cause the output oflogic function 52 to become a logic “1”.

As long as the output of logic function 52 remains a logic “0” duringregeneration enablement while the timing function times to the maximumtime set by C_T_MAX_STA_RGN, the output of OR logic function 56 remainsa logic “0”. Should the output of logic function 52 change to a logic“1” during that time, the output of OR logic function 56 would switchfrom a logic “0” to a logic “1”. Otherwise the output of OR logicfunction 56 will switch from a logic “0” to a logic “1” upon the timingfunction timing to the maximum time C_T_MAX_STA_RGN.

The output of OR logic function 56 therefore serves as one means toterminate an on-going passive regeneration based on length of theregeneration time and the condition of the DPF. It also assures thatonce passive regeneration has been enabled, it will be allowed tocontinue for some minimum time (set by C_T_MIN_STA_RGN), provided thatthe on-going regeneration is not aborted by a change in some otherparameter input to AND function 42 that was satisfied in order to enablethe passive regeneration to begin.

The various inputs to AND logic function 42 represented generally by thereference numeral 58 in FIG. 3A are parameters that serve to assure thatthe vehicle is and remains parked with the engine running at atemperature suitable for regeneration. Some degree of redundancy may beinherent in the use of numerous parameters for giving such assurance,and/or selection functions such as functions 60, 62 may be used toselect one parameter to the exclusion of another. Any given inputparameter may not be a direct input to AND logic function 42, but may beprocessed based on the specific condition that the logic value (LV) ofthe parameter represents. Hence it is the logic complement of someparameters that may be the direct input to AND logic function 42 byprocessing them with a NOT function as shown for several parameters,such as LV_VS_RUN, LV_BLS, and LV_BTS.

Two specific input parameters to AND logic function 42, LC_ENA_STA_RGNand LV_DISA_RGN, deserve detailed discussion.

Parameter LC_ENA_STA_RGN will change from a logic “0” to a logic “1”when the device (such as an instrument panel switch) that is operated bythe driver to initiate passive regeneration is operated.

Parameter LV_DISA_RGN is a logic signal from the inhibit strategy 40that will inhibit initiation of passive regeneration or terminate anon-going passive regeneration by change of state from a logic “0” to alogic “1”. The strategy for determining the logic value for LV_DISA_RGNis shown in FIG. 4 (a strategy constituting an independent inventionthat is the subject of Invention Submission D6047 identified in moredetail below). In the logic strategy of FIG. 3A, it is the complement ofLV_DISA_RGN (obtained by processing LV_DISA_RGN with a NOT logicfunction 64) that is the direct input to AND logic function 42 so thatthe condition “regeneration not inhibited (by strategy 40)” is one ofthe enablers of AND logic function 42 while the condition “regenerationinhibited” is a disqualifier of function 42 by itself.

Switch functions 66, 68 are associated with OR logic function 56 andLC_ENA_STA_RGN. The output of OR logic function 56 controls switchfunction 68 while LC_ENA_STA_RGN controls switch function 66.

Whatever the nature of the particular instrument panel device that thedriver operates to cause LC_ENA_STA_RGN to request a passiveregeneration via switch function 66, the effect on switch function 66 isto switch the output of the switch function to a logic “1” only longenough to assure that the data value provided by OR logic function 56will switch to a logic

When OR logic function 56 switches to a logic “0”, it operates switchfunction 68 to cause the latter to switch the logic “1” that switchfunction 66 is inputting to AND logic function 42 to a store 69 thatstores the logic “1” value. Consequently, when switch function 66reverts to the state it had been in prior to the passive regenerationrequest from the driver, it will continue to supply a logic “1” to ANDlogic function 42 because of the logic “1” in store 69.

Continued enablement of AND logic function 42 however now depends on ORlogic function 56. Because the latter logic function will remain a logic“0” for at least the minimum time set by C_T_MIN_STA_RGN regardless ofthe extent to which DPF 34 is loaded with trapped particulates, switchfunction 66 will continue to enable AND logic function 42 for at leastthat minimum time, and AND logic function 42 will continue to provide alogic “1” output provided that it is not disqualified by a change insome other input parameter.

If, after elapse of the minimum time set by C_T_MIN_STA_RGN, the loadingof the DPF still exceeds the level set by C_STATE_EGPB_PF_STOP_STA_RGN,regeneration will be allowed to continue until the earlier occurrenceof: DPF loading becoming less than that level and elapse of maximum timeset by C_T_MAX_STA_RGN.

Unless inhibited by Inhibit Strategy 40, an on-going regenerationterminates when the output of OR logic function switches from a logic“0” to a logic “1” to cause switch function 68 to once again supply alogic “0” to store 69. With switch 66 being in the state of transmittingthe contents of store 69 to AND logic function 42, the logic “0” fromthe store causes the output of AND logic function to switch to logic“0”.

In this way, a regeneration, once initiated by a regeneration request,must be terminated before a subsequent regeneration request can beeffective.

Once regeneration has been enabled by LV_ENA_STA_RGN becoming a logic“1”, set points for relevant engine parameters are reset in ECS 12 tovalues that will initiate passive regeneration as the engine continuesto run. Parameters whose set-points may be reset include: idle speed,main fuel injection timing, EGR valve position, turbocharger vaneposition, intake throttle position, post-injection fuel quantitiy, andpost-injection fuel timing. FIG. 3B shows parameter TBA, representingboost air temperature, setting the set point for engine idle speedduring passive regeneration N_SP_IS_STA_RGN.

Elapsed time of passive regeneration is represented by the parameterT_STA_RGN, and FIG. 3B shows that the data value for elapsed time ismade available to other portions of ECS strategy as appropriate.

The strategy for inhibiting regeneration is next described withreference to FIG. 4 which shows detail of Inhibit Strategy 40 forinhibiting Passive regeneration.

Strategy 40 provides the parameter LV_DISA_RGN as a logic signal thatwill inhibit initiation of passive regeneration or terminate an on-goingpassive regeneration by change of state from a logic “0” to a logic “1”.In other words whenever LV_DISA_RGN is a logic “1”, on-goingregeneration will be stopped and regeneration cannot commence.

When LC_INH_RGN, representing the state of a device, such as aninstrument panel switch, available to the driver to inhibitregeneration, changes from a logic “0” to a logic “1” to signaloperation of the device to a state requesting that regeneration beinhibited or that an on-going regeneration be stopped, a timer function90 is started and an AND logic function 92 is enabled. A maximum timefor inhibiting regeneration is set by a parameter C_T_MAX_INH_RGN. Acomparison function 94 compares the time elapsed on timer function 90with the parameter C_T_MAX_INH_RGN.

As long as the elapsed time is equal to or less than C_T_MAX_INH_RGN,the output of function 94 is a logic “1”. Once the elapsed time becomesgreater than C_T_MAX_INH_RGN, the output of function 94 becomes a logic“0”.

The output of function 94 forms one input to an AND logic function 96.The other input to AND logic function 96 is the output of anothercomparison function 98. The output from AND logic function 96 is thesecond input to AND logic function 92.

The two inputs to comparison function 98 are parameters STATE_EGBP_PFand C_STATE_EGBP_MIN_ENA_RGN_INH. The former parameter is an indicationof the extent to which DPF 34 is loaded with trapped particulates, andmay be measured in any suitably appropriate way. The latter parameterrepresents a value for DPF loading that distinguishes between enablingand unenabling the inhibiting of regeneration.

If STATE_EGBP_PF is less than C_STATE_EGBP_MIN_ENA_RGN_INH, the outputof function 98 is a logic “0”. If STATE_EGBP_PF becomes equal to orgreater than C_STATE_EGBP_MIN_ENA_RGN_INH, the output of function 98becomes a logic “1”.

Once inhibiting regeneration has been requested by LC_INH_RGN becoming alogic “1”, functions 94, 96, and 98 coact to force the output of logicfunction 96 to logic “1” while timing function 90 is timing toward themaximum time set by C_T_MAX_INH_RGN, provided that the DPF is not loadedbeyond the level set by C_STATE_EGBP_MIN_ENA_RGN_INH. The coactionenables function 96 to cause LV_DISA_RGN to be set to logic “1”,provided that the DPF is not loaded beyond the level set byC_STATE_EGBP_MIN_ENA_RGN_INH. In other words, regeneration will beinhibited.

Regeneration would not be inhibited if the DPF were loaded to the extentthat inhibiting regeneration could potentially damage the DPF.

In any event, regeneration will be inhibited at most for the timeallowed by C_T_MAX_INH_RGN.

Whatever the nature of the particular instrument panel device that thedriver operates to cause LC_INH_RGN to request a regeneration inhibit,such a request, unless prohibited by the level of particulates in theDPF, switches LV_DISA_RGN to a logic “1” that consequently acts via NOTlogic function in FIG. 3A to disqualify AND logic function 42. The logicvalue “1” that is provided by LC_INH_RGN lasts only momentarily, justlong enough to assure the inhibit.

LC_INH_RGN momentarily sets the state of a switch function 99 to a logic“1”, applied to AND logic function 92 as mentioned above. The logic “1”is also returned to a second switch function 101 whose state iscontrolled by the complement of the output of AND logic function 96, thecomplement being provided by a NOT logic function 103.

Assuming that AND logic function 96 has been set to logic “1” underappropriate conditions specified above, the logic “0” to switch function101 via NOT logic function 103 causes that switch function to switch thelogic “1” that is being returned from switch function 99 to a store 105.In this way, switch function 99 is latched to continue the logic “1”output even after LC_IHN_RGN ceases to continue a logic “1” input toswitch function 99, provided that the conditions that are causing ANDlogic function 96 to output a logic “1” continue to exist.

Because the function of logic function 98 is essentially to set aninitial condition for allowing regeneration to be inhibited, it couldcause discontinuance of an on-going inhibit before timing function does,but it would not necessarily initiate a regeneration upon causingdiscontinuance of an on-going inhibit.

FIGS. 5, 6, and 7 show a modified inhibit strategy 40A that is thesubject of the inventors' commonly assigned patent application having acommon filing date and entitled SYSTEM AND METHOD FOR INHIBITINGREGENERATION OF A DIESEL PARTICULATE FILTER_(Attorney Docket D6047).While inhibit strategy 40A is capable of being activated by adiscretionary inhibit request from a device such as the instrument panelswitch used by a person to inhibit passive regeneration while thevehicle is stationary, strategy 40A utilizes vehicle speed as a factorfor determining if regeneration will be inhibited. Therefore strategy40A should be understood to be capable of inhibiting regeneration whilea vehicle is moving, provided certain conditions are satisfied, and notonly to inhibit an on-going passive regeneration while the vehicle isstationary.

The parameter STATE_EGBP_PF is a measurement or estimate of the sootload contained in DPF 34.

A parameter LV_PF_INH_RGN_EXT is an input obtained from a vehicle bodycontroller for enabling the inhibit function.

A parameter LV_PF_INH_RGN_ENA_VAR is a programmable parameter forenabling the inhibit function.

A parameter LC_PF_INH_RGN represents the state of a manual calibrationswitch that enables personnel who are calibrating the system (commonlycalled calibrators) to calibrate certain portions of the system andassociated logic.

Parameters LV_PF_INH_RGN_EXT, LV_PF_INH_RGN_ENA_VAR, and LC_PF_INH_RGNare inputs to AND logic functions 110, 112 as shown in FIG. 5.

A parameter C_T_MAX_INH_PF_RGN represents a maximum time limit for whichthe inhibit function, when allowed to be active, may be inhibited.

A parameter VS represents vehicle speed obtained from a vehicle speedsensor. Conversion to proper units, such as shown in FIG. 5, may beperformed if necessary.

A parameter VS_MAX_PF_ENA_RGN_INH_CUS represents a vehicle speed thatdefines a boundary between a first speed range within which inhibitstrategy 40A is not allowed to be active and a second speed range ofhigher speeds within which inhibit strategy is automatically allowed tobe active.

A parameter VS_MIN_PF_ENA_NORM_RGN_CUS represents a vehicle speed thatdefines a boundary between the second speed range and a third speedrange of still higher speeds within which an intentional inhibit requestby the driver of the vehicle will cause inhibit strategy 40A to beactive.

A parameter VS_MAX_PF_ENA_MAN_RGN_CUS represents a vehicle speed thatdefines a boundary between the third speed range and a fourth speedrange of still higher speeds within which inhibit strategy 40A is notallowed to be active.

A range of DPF soot loads is relevant to inhibit strategy 40A. Aparameter C_MIN_STATE_EGBP_PF_INH_EXIT represents the lower limit of therange and a parameter C_MAX_RGN_INH_STATE_EGBP_PF represents the upperlimit of the range.

Parameters C_VS_PF_NORM_RGN_HYS_ON and C_VS_PF_NORM_RGN_HYS_OFF impart ahysteresis band to parameter VS_MAX_PF_ENA_RGN_INH_CUS for enlarging oneof the second and third speed ranges at the expense of the otherdepending on the direction of vehicle speed changes in a speed rangespanning the speed represented by parameter VS_MAX_PF_ENA_RGN_INH_CUS.This hysteresis is depicted in FIG. 5 by the reference numeral 114.

FIG. 5 shows the parameters LV_DISA_RGN and LV_DISA_RGN1 as outputs.

FIG. 6 pictorially portrays the four speed ranges as a Vehicle SpeedIndex where VS Index 1 equates to VS_MAX_PF_ENA_RGN_INH_CUS, VS Index 2equates to VS_MIN_PF_ENA_NORM_RGN_CUS, and VS Index 3 equates to VS_MAXPF_ENA MAN_RGN_CUS. The hysteresis band represented by numeral 114 isshown bounding VS Index 2.

The control system allows the parameters shown in FIG. 6 to be set. VSIndex 1 is a speed threshold below which inhibit strategy 40A is notallowed to be active, for example a speed around one mile per hour. Forspeeds between VS Index 1 and VS Index 2, for example a speed aroundfifteen miles per hour, the inhibit strategy is automatically allowed tobe active. For speeds between VS Index 2 and VS Index 3, for example aspeed around twenty-five miles per hour, the inhibit strategy is allowedto be active when requested by the driver of the vehicle. For speedsgreater than VS Index 3, the inhibit strategy is not allowed to beactive.

FIG. 7 shows a state diagram 120 comprising a NOT INHIBITED state 122,an INHIBIT ACTIVE state 124, and an INHIBIT PROHIBITED state 126.

If the vehicle speed is less than VS Index 1 or greater than VS Index 3,strategy 40A is not allowed to be active, meaning that it cannot inhibitregeneration (state 122).

VS Index 1 has a non-zero value so that activation of the passivestationary regeneration strategy continues to be allowed when thevehicle is parked.

If vehicle speed is within the range between VS Index 1 and VS Index 2,strategy 40A automatically becomes active, meaning that regenerationwill be automatically inhibited provided that certain conditions aresatisfied (state 124). If vehicle speed is within the range between VSIndex 2 and VS Index 3, strategy 40A will not become active unless thedriver is intentionally requesting that regeneration be inhibited,meaning that regeneration will be inhibited as requested, provided thatcertain conditions are satisfied (state 126).

FIG. 8 shows a passive regeneration strategy 130 that utilizes many ofthe same parameters as the passive regeneration strategy of FIG. 2 asinputs to an Authorize strategy 132. Those parameters include: EngineOil Temperature TOIL; Engine Coolant Temperature TCO, Engine RunningLV_RUN_ENG, Brake Light Switch LV_BLS, Brake Test Switch LV_BTS,Accelerator Position PV_AV, Automatic Transmission LV_AT, and DisallowRegeneration LV_DISA_RGN. Other parameters used by strategy 130, but notby the strategy of FIG. 2, are: VS Index 1 VS_MAX_ENA_STA_RGN[PP] (sameas VS_MAX_PF_ENA_RGN_INH_CUS); Vehicle Speed VS; Drivetrain Disengaged(for automatic transmission) LV_DT; Drivetrain Disengaged (for manualtransmission) LV_DT_TRAN (for manual; and Power Takeoff ActivePTO_SIG_SEL. (Note: the [PP] suffix denotes a programmable parameter.)

Another parameter used by strategy 130, but not by the strategy of FIG.2, is SOOT_LOAD_CHECK, a parameter provided at a soot load check outputof an Activate strategy 134 shown in detail in FIG. 10. Other portionsof strategy 130 interface Authorize strategy 132 with a Manager strategy136.

One output parameter of Manager strategy 136 is T_STA_RGN representingelapsed time of regeneration. Two other output parameters areLV_ENA_MAN_RGN and LV_ENA_MAN_RGN_CMPL.

FIG. 9 shows more detail of Authorize strategy 132 in the same way asFIG. 3A shows more detail of strategy 38.

TOIL and TCO are selectable by a switch function 62 based on a parameterLC_TEMP_INP_SWI_STA_RGN. This allows a calibrator to select one of thetwo parameters as best representative of engine temperature. Acomparison function 62A compares the selected parameter with a referencetemperature C_TEMP_MIN_THD_STA_RGN. When the temperature represented bythe selected parameter exceeds the reference temperature, the input toAND logic function 42 is a logic “1” to indicate that sufficiently highengine temperature exists to support regeneration, otherwise a logic“0”.

A comparison function 63 compares Vehicle Speed VS with a parameterVS_MAX_ENA_STA_RGN[PP] representing the reference speed VS Index 1. Whenthe vehicle speed is less than or equal to the reference speed VS Index1, function 63 provides a logic “1” to AND logic function 42, otherwisea logic “0”.

A comparison function 63A compares Accelerator Position PV_AV with aparameter C_PV_MAX_THD_STA_RGN, the latter representing a maximumallowable accelerator input relative to low idle position. When theaccelerator position is at, or within a defined range of, low idleposition, function 63A provides a logic “1” to AND logic function 42,otherwise a logic “0”. This is to assure that the driver is notoverriding low idle speed control by depressing the accelerator pedal.

A comparison function 63B compares Power Takeoff Active PTO_SIG_SEL witha logic “0”. When the power takeoff (if present) is not active, or if nopower takeoff is present, function 63B provides a logic “1” to AND logicfunction 42, otherwise a logic “0”.

In the case of a vehicle having a manual transmission, no automatictransmission is present, and therefore a switch function 63C makes thelogic complement of LV_DT_TRAN to the exclusion of the LV_DT effectiveas an input to AND logic function 42. In the case of a vehicle having anautomatic transmission, switch function 63C makes LV_DT to the exclusionof the logic complement of LV_DT_TRAN effective as an input to AND logicfunction 42. In either of these two cases, the input to AND logicfunction 42 from switch function 63C is a logic “1” only when thedrivetrain is disengaged from the engine, otherwise a logic “0”.

Only when all inputs to AND logic function 42 are logic “1's” is theoutput LV_ENA_AUTH_MAN_RGN a logic “1”, otherwise a logic “0”.LV_ENA_AUTH_MAN_RGN may therefore be considered as authorizing, orallowing, passive regeneration. Regeneration will commence however onlywhen activated by Activate strategy 134, detail of which is describedwith reference to FIG. 10.

Activate strategy 134 comprises a comparison function 138, an OR logicfunction 140, an AND logic function 142, a second OR logic function 144,and a switch function 146. LC_ENA_STA_RGN is an input from a switch thatallows calibrators to activate stationary regeneration duringengine/vehicle development.

Both the parameter SOOT LOAD CHECK and the parameter LV_MAN_RGN_ACT atan activate output of Activate strategy 134 must be set to logic “1's”in order to activate the regeneration strategy. When parameterLC_ENA_STA_RGN is set to a logic “1” by a calibrator, OR logic function140 causes SOOT LOAD CHECK to also be a logic “1” input to AND logicfunction 420R logic function 144, acting via switch function 146 alsocauses LV_MAN_RGN_ACT to be a logic “1”. LV_TEST_RUN_MAN_RGN₁ andLV_TEST OUT_MAN_RGN1 are used by a service tool for diagnostic purposesby service personnel.

LV_ENA_STA_RGN_EXT1 is the input, such as an instrument panel switch, orother external input, that is actuated by any personnel, such ascalibrators, service personnel, or the driver of the vehicle, to requeststationary passive regeneration.

Comparison function 138 compares STATE_EGBP_PF with a referenceparameter identified simply by the numeral “3” The reference parameterdefines some threshold level of particulates that must be present in theafter-treatment device in order for SOOT_LOAD_CHECK to become a logic“1”. This avoids unnecessary regenerations that might otherwise berequested by personnel via parameter LV_ENA_STA_RGN_EXT1.

The parameter Activate (same as LV_MAN_RGN_ACT) is one input to thelogic arrangement that interfaces Activate strategy 134 with Managerstrategy 136. The logic arrangement comprises an OR logic function 148,two comparison functions 150, 152, a store 154, and a flip-flop 156. Theset output of flip-flop 156 is the parameter LV_ACT_MAN_RGN that formsone input to Manager strategy 136.

There are four additional inputs to Manager strategy 136: a parameterC_T_MAX_STA_RGN representing a maximum allowed duration for a stationaryregeneration (Max_time); a parameter C_T_MIN_STA_RGN representing aminimum mandatory duration for a stationary regeneration (Min_time); anoutput from a comparison function 158 (lv_dP_exit); and an output from adelay function 162 (LV_ENA_AUTH_MAN_RGN).

A comparison function 158 compares a parameterC_STATE_EGBP_PF_STOP_STA_RGN and STATE_EGBP_PF and provides the resultas the input lv_dP_exit to Manager strategy 136.

The output parameter LV_ENA_AUTH_MAN_RGN of Authorize strategy 132 isone input to an AND logic function 160 having a parameterLV_FEAT_STA_RGN[PP] as its other input. The latter parameter isprogrammed into the control system of any engine that is equipped withthe stationary passive regeneration strategy. The inverse of parameterLV_ENA_AUTH_MAN_RGN is provided by a NOT logic function 164 as aparameter LV_INH_MAN_RGN.

Manager function 136 operates in a similar manner to the strategyembodied in FIG. 3B described earlier.

When Authorize strategy 132 is not authorizing regeneration and anengine has the capability for passive stationary regeneration, parameterLV_ENA_AUTH_MAN_RGN is a logic “0”, preventing Manager strategy 136 frombecoming operational so that no regeneration occurs.

When Authorize strategy 132 authorizes regeneration and an engine hasthe capability for passive stationary regeneration, parameterLV_ENA_AUTH_MAN_RGN becomes a logic “1”, satisfying one condition forallowing Manager strategy 136 to become operational so that passivestationary regeneration can occur. Before that operational capabilitycan be achieved, a second condition must be satisfied. That condition isthat flip-flop 156 be switched from reset to set so as to also provide alogic “1” input to Manager strategy 136. The switching of flip-flop 156from logic “0” to logic “1” is controlled by Activate strategy 132 andsome of the interface functions between the Activate and Managerstrategies.

Provided that the after-treatment device has a sufficient amount oftrapped soot that makes regeneration appropriate as determined byfunction 138, strategy 134 sets SOOT LOAD CHECK to logic “1”. WhenLV_ENA_STA_RGN_EXT is set to logic “1” by the input device associatedwith it, strategy 134 sets LV_MAN_RGN_ACT to a logic “1”. With store 154storing the prior logic “0” value, the change in LV_MAN_RGN_ACT detectedby function 152 functioning as a rising edge detector to apply a logic“1” to the set input of flip-flop 156 causes the flip-flop to beswitched from reset condition to set condition. The content of store 154also changes to a logic “1” so that with LV_MAN_RGN_ACT remaining alogic “1”, the output of function 152 switches back to logic “0” afterit has set flip-flop 156.

Unless the regeneration strategy ceases being activated by eitherAuthorize strategy 132 or Activate strategy 134 terminating activation,regeneration will occur for at least the minimum time set by parameterC_T_MIN_STA_RGN. If the soot level in the after-treatment device has notbeen reduced to a level below that set by parameterC_STATE_EGBP_PF_STOP_STA_RGN after the minimum time, regeneration willcontinue until the earlier of: a) soot level in the after-treatmentdevice being reduced to a level below that set by parameterC_STATE_EGBP_PF_STOP_STA_RGN, and b) elapse of maximum time allowed forregeneration C_T_MAX_STA_RGN, unless the regeneration strategy ceasesbeing activated by either Authorize strategy 132 or Activate strategy134.

Should Activate strategy 134 de-activate the regeneration strategy,function 150 will function as a falling edge detector to cause flip-flop156 to be reset and as a result cause Manager strategy 136 to end theregeneration. When Manager strategy 136 ends a regeneration by causingparameter LV_ENA_MAN_RGN_CMPL to change from logic “0” to logic “1”, thechange acts via OR function 148 to reset flip-flop 156. Even withAuthorize strategy 132 continuing to authorize activation of theregeneration strategy, activation cannot reoccur unlessLV_ENA_STA_RGN_EXT is again set to a logic “1” after having first beenreset to logic “0”.

FIG. 11 shows the operational states that have just been described forthe strategy of FIG. 8. The state bearing the heading NOT RUNNING is thestate that exists when the regeneration strategy is not active. Thestate bearing the heading RUNNING is the state that exists when theregeneration strategy is active. At entry into the RUNNING state, asub-state “Regen incomplete” is entered. When regeneration has becomecompleted for any one of the reasons explained above, a sub-state “Regencompleted” is entered. A slight delay is present in the execution of thestrategy before the state reverts to the NOT RUNNING state so as toallow time for parameter inputs to the manager strategy to assumeappropriate values consistent with de-activating the strategy as acondition precedent to a subsequent activation.

When parameter LV_ENA_MAN_RGN is set to a logic “1”, it causes theengine to operate in a way that conditions exhaust gases for causingnitrogen dioxide-based regeneration of the after-treatment device. Itdoes so via certain actuators. Various actuators can be ramped-in atvarious times and rates while the stationary regeneration strategy isactive.

FIG. 12 shows one example of actuator set-point “ramping” for main fuelinjection timing SOI (start of injection). Upon regeneration becomingactive, LV_ENA_MAN_RGN_PF switches from logic “0” to logic “1”. Atime-based function 172 is used to control the set-point for SOI. TheSOI_MAIN1_TIMEBASE table can be constructed in such a way that itsoutput may be shaped to achieve the best performance possible. The othertwo time-based functions 174, 176 provide correction of the SOI valuefrom function 170 to compensate for variations in ambient temperatureand ambient atmospheric pressure (elevation above sea level), thecorrection being performed by a portion 178 of the engine controlsystem. The substituted value for SOI set-point from portion 178 isswitched into the fuel control portion of the engine control system viaa switch function 180.

With appropriate adaptation, the example of FIG. 12 can be adopted forany or all of: engine idle speed, exhaust gas recirculation (EGR) valveposition set-point, exhaust gas backpressure set-point, turbochargervane position pre-control, fuel injection rail pressure set-point,intake throttle position set-point, and injection mass and injectiontiming for pilot injections and post-injections of fuel.

Each of the parameters/actuators mentioned can be activated at times andrates independent of the others. When stationary regeneration iscomplete, these parameters may be ramped back to their “normal” valuesusing the respective “TIMEBASE” table before LV_ENA_MAN_RGN_PFtransitions back to logic “0”.

An example of an implementation is given for engine low idle speedset-point. At T_STA_RGN=0 seconds, low idle speed is ramped to a valueof 1200 rpm or so depending on various conditions. The intake throttleis ramped to a nearly closed position at T_STA_RGN=0 seconds.

SOI_MAIN1 is held at a constant value for approximately 60 seconds afterthe throttle and idle speed have been ramped until conditions in theDiesel Oxidation Catalyst (DOC) are favorable for converting combustionby-products into exhaust gases suitable to passively burn soot out ofthe diesel particulate filter (DPF). When the DOC is ready, main fuelinjection timing is retarded (by using SOI_MAIN1_TIMEBASE) to producemore of the combustion by-products that will create more heat and gasesnecessary for passive regeneration of the DPF.

FIGS. 13, 14, and 15 are presented to show, without detaileddescription, another example of passive regeneration strategy that islargely the functional equivalent of the preferred embodiments that havebeen described in detail above. The Figures comprise a Passive DPFRegeneration Control Strategy 38B, and an Inhibit Strategy 40B forInhibiting Passive DPF Regeneration Control Strategy 38B, and a SpecialMessages Section 41B. The active regeneration strategy is not shown inFIGS. 13, 14, and 15.

While a presently preferred embodiment of the invention has beenillustrated and described, it should be appreciated that principles ofthe invention apply to all embodiments falling within the scope of theinvention that is defined as follows.

1. A diesel engine comprising: an exhaust system through which exhaustgases created by combustion in combustion chambers pass to atmosphereand which comprises an after-treatment device that treats the gasesbefore leaving the exhaust system but that at times requiresregeneration by elevation of temperature of the gases to a regenerationtemperature range; an engine control system for processing various datato control various aspects of engine operation for conditioning thegases to cause regeneration of the after-treatment device; wherein thecontrol system comprises a first regeneration strategy for conditioningthe gases to cause oxygen-based regeneration of the after-treatmentdevice and a second regeneration strategy for conditioning exhaust gasesto cause nitrogen dioxide-based regeneration of the after-treatmentdevice when the engine is operating at low idle speed in accordance witha low idle speed control strategy.
 2. A diesel engine as set forth inclaim 1 wherein the control system comprises a strategy for selectivelyinhibiting one of the regeneration strategies.
 3. A diesel engine as setforth in claim 2 wherein the strategy for selectively inhibiting one ofthe regeneration strategies comprises a strategy for inhibiting thefirst regeneration strategy from being used when the after-treatmentdevice is being regenerated by the second regeneration strategy.
 4. Adiesel engine as set forth in claim 1 comprising aregeneration-initiation input to the control system for initiatingregeneration of the after-treatment device by the second regenerationstrategy.
 5. A diesel engine as set forth in claim 4 wherein the controlsystem comprises a timing function that once regeneration of theafter-treatment device by the second regeneration strategy has beeninitiated, provides for nitrogen dioxide-based regeneration of theafter-treatment device to continue for at least as long as a selectedminimum time limit.
 6. A diesel engine as set forth in claim 5 whereinthe control system comprises an additional control that is effective,once nitrogen dioxide-based regeneration of the after-treatment devicehas continued for at least the minimum time limit, to terminate theon-going regeneration upon the first to occur of a) disclosure that theafter-treatment device has been regenerated sufficiently to no longerrequire regeneration and b) a selected maximum time limit.
 7. A dieselengine as set forth in claim 4 comprising additional inputs to thecontrol system that are used by the control system, once regeneration bythe second regeneration strategy has been initiated, to conditionnitrogen dioxide-based regeneration of the after-treatment device onsatisfaction of certain conditions precedent to such initiation.
 8. Adiesel engine as set forth in claim 1 wherein the control systemcomprises a first set of data values for set-points of certain engineparameters used by the control system to cause oxygen-based regenerationof the after-treatment device, and a second set of data values forset-points of those certain engine parameters used by the control systemto cause nitrogen dioxide-based regeneration of the after-treatmentdevice.
 9. A diesel engine as set forth in claim 8 wherein the certainengine parameters include one or more of engine idle speed, main fuelinjection timing, EGR valve position, turbocharger vane position, intakethrottle position, post-fuel injection quantity, and post-injection fueltiming.
 10. A diesel engine as set forth in claim 1 further including awheeled motor vehicle that is propelled by the engine, and comprisinginputs to the control system that are used by the control system tocondition initiation of nitrogen dioxide-based regeneration of theafter-treatment device by a regeneration-initiation input to the controlsystem on satisfaction of certain conditions precedent to suchinitiation, including a condition of a regeneration-initiation devicebeing operated, a condition of the vehicle being stationary, and acondition of engine temperature sufficiently high to initiate nitrogendioxide-based regeneration.
 11. A diesel engine as set forth in claim 10wherein the strategy for selectively inhibiting one of the regenerationstrategies comprises inhibiting the first regeneration strategy frombeing used when the after-treatment device is being regenerated by thesecond regeneration strategy.
 12. A diesel engine as set forth in claim10 wherein the after-treatment device comprises a diesel particulatefilter that requires regeneration to burn off trapped diesel particulatematter.
 13. A method for regenerating an exhaust after-treatment devicein an exhaust system of a diesel engine, the method comprising:operating the engine to create exhaust gases for causing nitrogendioxide-based regeneration of the after-treatment device uponconcurrence of conditions precedent that include aregeneration-initiation device for initiating such a regeneration beingin a condition for initiating such a regeneration, the engine operatingat a low idle speed in accordance with a low idle speed controlstrategy, and engine temperature condition being sufficiently high toinitiate nitrogen dioxide-based regeneration.
 14. A method as set forthin claim 13 wherein the engine propels a wheeled motor vehicle, and themethod comprises operating the engine to create exhaust gases forcausing nitrogen dioxide-based regeneration of the after-treatmentdevice upon the condition of the vehicle being stationary being afurther condition precedent for causing nitrogen dioxide-basedregeneration of the after-treatment device.
 15. A diesel enginecomprising: an exhaust system through which exhaust gases created bycombustion in combustion chambers pass to atmosphere and which comprisesan after-treatment device that treats the gases before leaving theexhaust system but that at times requires regeneration by elevation oftemperature of the gases to a regeneration temperature range; an enginecontrol system for processing various data to control various aspects ofengine operation for conditioning the gases to cause regeneration of theafter-treatment device; wherein the control system comprises aregeneration strategy for conditioning exhaust gases to cause nitrogendioxide-based regeneration of the after-treatment device when the engineis operating at low idle speed in accordance with a low idle speedcontrol strategy.
 16. A diesel engine as set forth in claim 15 furtherincluding a wheeled motor vehicle that is propelled by the engine, andcomprising inputs to the control system that are used by the controlsystem to condition initiation of nitrogen dioxide-based regeneration ofthe after-treatment device by a regeneration-initiation input to thecontrol system on satisfaction of certain conditions precedent to suchinitiation, including a condition of a regeneration-initiation devicebeing operated, a condition of the vehicle being stationary, and acondition of engine temperature sufficiently high to initiate nitrogendioxide-based regeneration.